Lubricant composition



Patented June 8, 1943 LUBRICANT CODHOSITION Raphael Rosen, Elizabeth, N.l, assignor to Standard Oil Development Company, a corporation ofDelaware No Drawing. Application January 2, 1941, Serial No. 372,839

1 Claim.

The present invention relates to an improverent in lubricants andsimilar oils, as well as ther hydrocarbon materials, especially inrepect to resistance to decomposition at elevated emperatures andoxidizing conditions such as re encountered in internal combustionengines. he invention will be fully understood from the escription whichfollows.

It has been found that mineral oil lubricants in be greatly improvedwith respect to their ability against decomposition, especially undereat and oxidizing conditions, by the addition ieretc of small amounts ofcertain substances. 1 the present case, a new group of substances asbeen discovered which are particularly effecve in reducing the oxidationof oils at the elettecl temperatures encountered in internal comistionengines, 1. e., at temperaturesof 200 C. higher. This group ofsubstances comprises 1e inorganic salts of quaternary ammonium lses.Such compounds are soluble in mineral is to only a small extent when thenitrogen am of the compound is attached to short hywocarbon radicals.Greater solubility can be iparted to the compound by increasing the ngthof the aliphatic radicals and compounds ith a total of at least 12carbon atoms in all the aliphatic radicals are most desired for themoose of the present inventior'i. Compounds lite insoluble may, however,be used by being spersed in the oil or when dissolved by the aid amutual solvent.

In its broadest aspects, the preferred class of :W addition agentsincludesthe compounds Wing the formula:

iere R is a hydrocarbon radical, for example, L alkyl, cycloalkyl, arylor aralkyl radical, X is L inorganic acid radical, and m is an integer,or or less, chosen according to the valencies the R groups to satisfyfour bonds of the trogen atom. The various R groups may be nilar ordissimilar. The radicals R may conin substituent atoms, for example,halogen, trogen, phosphorus, oxygen or sulfur, or subtuent groups, forexample, hydroxyl, aroxy, :oxy, keto, amino or mercapto groups. Theeferred compounds are those in which the R :nups are alkyl groups. Themost preferred mpounds are those in which the total number carbon atomsin all of the hydrocarbon rad- '.ls is at least 12 and preferably atleast 16, if ailable. The acid radical 'may be of any type inorganicacid radical, but the salts most preferred are the halides, phosphates,phosphites, thiophosphates, thiophosphites, cyanates and thiocyanates ofthe ammonium bases. It is desirable to select compounds which aresoluble in lubricating oil to the extent of at least 0.5% attemperatures above 30 F. Typical examples of suitable compounds aretetra-n-butyl ammonium iodide, tetra-'n-butyl ammonium bromide,octadecyltributyl ammonium iodide, benzyloctadecyldimethyl ammoniumchloride, octadecyl benzyl dimethyl ammonium chloride, cyclohexyltriisobutyl ammonium phosphite, phenyl tridecyl ammonium thiocyanate,triethanol octadecyi ammonium sulfite, methyl pyridonium sulfide andchlorethyl tributyl ammonium nitrate. In addition to the above, suitableexamples include the nitrites, sulfites, hypophosphites, borates,stannates, arsenates, arsenites, chromates and chromites of variousquaternary ammonium bases.

The new class of antioxidant compounds are advantageously added to theoils in concentrations ranging from 0.05 to 5%, but the quantitygenerally preferred is about 0.1 to about 1%.

In general, the base stock to be used in the preparation of thelubricants of the present invention may be any refined minerallubricating oil, preferably having a viscosity from 40 to 150 secondsSaybolt at 210 F., and suitable base stocks include those of highparaflinicity and high viscosity index, such as those which have aviscosity index of or more, as well as low parafiin and low viscosityindex oils. Base stocks comprising greases, fatty oils or synthetic oilsmay also be employed.

The addition agents of this invention do not have any detrimentaleffects on thephysical character of the lubricating oil to which theyare added, such as viscosity, gravity and flash point. The new additivesmay be used as the sole blending agents, or they may be added with otheringredients, such as oiliness agents, film strength modifiers, pourdepressants, thickeners, viscosity index improvers, detergents, sludgedispersers, solvents, dyes, and the like.

The compounds described above may be used as oxidation inhibitors andimproving agents in similar concentrations in other lubricating oilproducts, such as lubricating greases and extreme pressure lubricants.

The value of the antioxidants of the present invention when used inlubricating oil blends has been determined by several standard tests,including the oxygen absorption test, the cone test and the Slighoxidation test.

The oxygen absorption test is carried out by bubbling a known amount ofoxygen through cc. of the lubricating oil maintained at 200 C. Theoxygen is continuously recycled. At the end of succeeding minute periodsthe amount of oxygen absorbed by the oil is measured. The results aregiven as the number oi! cubic centimeters of oxygen absorbed during eachof these 15 minute periods.

The cone test, which is a means for determining the tendency of an oilto deposit solid material upon heated metallic surfaces, is carried outby slowly dropping oil to be tested over a heated metal cone having acircumferential groove milled out in a screw iashionon the periphery soas to allow a time of contact of about one minute between the heatedmetallic surfaces and the oil. A total volume of 60 cc. of oil isdropped from a dropping funnel during a period of two hours, thetemperature of the cone being maintained at 250 C. The cone is thenwashed in naphtha to remove adhering oil and the total depositdetermined by difference in weight.

The Sligh oxidation test is carried out by heating 10 grams of the oil,contained in a stoppered conical flask from which the air has beendisplaced by oxygen, at 200 C. in an oil bath for 2 /2 hours. The numberof milligrams of asphaltenes formed, determined by a solution of the oilin precipitation naphtha and filtration through a Gooch crucible, istermed the Sligh number of the oil.

The value of the antioxidants of the present invention as additionagents for lubricating oils may be illustrated by the following example.

. Example A refined mineral lubricating oil of S. A. E. grade wasblended, separately, with 0.2% of tetra-n-butyl ammonium iodide and 0.2%0!- tetra-n-butyl ammonium bromide, and the blends thus formed, as wellas a blank sample of thebase oil, were submitted to the cone test, theoxygen absorption test and the Bligh oxidation test,

The present invention is not to be considered as limited by the hereindescribed example, which is given by way of illustration only, but it isto be limited solely by the terms of the following claim.

I claim:

A lubricant containing dissolved therein 0.05% to 5% of tetra-n-butylammonium iodide.

RAPHAEL ROSEN.

